[2-[4-[4-(chlorophenyl)phenylmethyl]-1-piperazinyl]ethoxy]acetic acid also known by the generic name of cetirizine is a non-sedating type histamine H1-receptor antagonist and is used in the treatment of allergic syndromes. It's pharmacological and medicinal properties have been described in the literature, C. De. Vos et. Al., Ann. Allergy 59, 278, 1987; L. Juhlin et. Al, J. Allergy Clin. Immunol., 80, 80, 599 (1987).
Canadian Patent 1.199,918 describes the synthesis of cetirizine following two different routes as illustrated in Scheme 1: ##STR2##
All the starting materials require for these 2 routes are not commercially available and accordingly these two routes involve a multi step process resulting in low overall yields.
Canadian Patent 1,317,300 teaches a process for preparing cetirizine by reaction of 1-[(4-chlorophenyl)phenylmethyl-piperazine with an haloethoxyacetonitrile. Again as all the starting materials are not commercially available and it results in a multi step process which generally is costly.
Canadian Patent 1,320,732 relates to a process for preparing cetirizine by reacting [2-[4-[4-(chlorophenyl)phenylmethyl]-1-piperazinyl]-ethanol with an alkali metal haloacetate. Again the starting alcohol results from a multi step process adding to the cost of the whole process and decreasing the overall yield.
There is a need to find an economical process for the production of these [2-[4-[4-(chlorophenyl)phenylmethyl]-1-piperazinyl]ethoxy]acetic acid derivatives which will allow for higher yields than those obtained in the prior art.